J. Dekker et al., WEEDY ADAPTATION SETARIA SPP .4. CHANGES IN THE GERMINATIVE CAPACITY OF S-FABERII (POACEAE) EMBRYOS WITH DEVELOPMENT FROM ANTHESIS TO AFTERABSCISSION, American journal of botany, 83(8), 1996, pp. 979-991
Studies were conducted evaluating germinability states in giant foxtai
l (Setaria faberii) embryos, as well as surrounding tissues (hull, car
yopsis), with germination assays. Further, seed age, fascicle arrangem
ent, flowering patterns, and elongation in the inflorescence were eval
uated. Both qualitatitive and quantitative morphological observations
of the hull and the caryopsis were revealed by precisely determined fe
rtilized spikelet age from anthesis until after seed abscission. Red c
oloration of the placental pad at approximate to 11 d after anthesis i
s probably a morphological indicator of physiological maturity. Germin
ability of giant foxtail embryos changed with development. Four qualit
atively different types of embryo germination were observed during dev
elopment of the seed: early disorganized callus growth at the basal, c
oleorhizal end of the embryo; germination of immature embryos with sho
rtened and thickened axes; germination of the scutellum; and germinati
on and growth of the coleoptile and coleorhiza in embryos aged 7 d aft
er anthesis and older. Axis-specific embryo germinability was also obs
erved. Inhibition of the embryo could be localized to the coleoptile,
the coleorhiza, or both. These studies provide evidence for a complex
model of germinability regulation based on the independent, asynchrono
us actions of the embryo, caryopsis, and hull compartments, as well as
on their dependent, synchronous action. These studies provide evidenc
e for a dynamic, developmental model of giant foxtail germinability re
gulation resulting in phenotypes with a wide range of germinability sh
ed from an individual panicle. These diverse germinability phenotypes
are found at all stages of development, but particularly when the seed
is shed and the soil seed bank is replenished.